Safety monitoring circuit for electrosurgical unit

• US 4,231,372 A
• Filed: 11/04/1974
• Issued: 11/04/1980
• Est. Priority Date: 11/04/1974
• Status: Expired due to Term

• Current Assignee: Valleylab Inc. (Medtronic Plc)
• Original Assignee: Valleylab Inc. (Medtronic Plc)
• Inventors: Newton, David W.
• Primary Examiner(s): Cohen, Lee S.
• Application Number:
  US05/520,269
• Time in Patent Office: 2,192 Days
• Field of Search: 128/303.13, 128/303.14, 128/303.17, 128/303.18, 128/2.1 P, 128/2.06 A, 128/908, 317/18 A, 317/18 B, 317/18 D, 317/18 R, 317/31, 361/42
• US Class Current: 606/35
• CPC Class Codes: A61B 18/1233 with circuits for assuring patient safety
• CPC Class Codes: A61B 18/16 Indifferent or passive electrodes for grounding
• CPC Class Codes: G01R 31/50 Testing of electric apparatus, lines, cables or components for short-circuits, continuity, leakage current or incorrect line connections testing of sparking plugs H01T13/58
• CPC Class Codes: G01R 31/54 Testing for continuity
• CPC Class Codes: H02H 3/162 for ac systems

Abstract

A safety monitoring circuit for use in an electrosurgical unit is disclosed. The circuit is useful to indicate a fault in the return path between an RF source and a patient electrode in contact with a patient to prevent electrical burns to the patient that can occur due to improper patient contact with the patient electrode or a break in the return path. The circuit includes a current sensor connected in series in the return path to the RF source, which sensor provides an output indicative of the sensed current that is coupled through a DC amplifier to a comparator, the comparator providing an output only if a predetermined threshold is exceeded. When a comparator output is provided, a timer is triggered to energize, for a predetermined period of time, an alarm to indicate a sensed fault and/or actuate disabling circuitry to terminate application of electrical energy to the active electrode utilized in electrosurgery for cutting or coagulation.

Claims

1. A radio-frequency electrosurgical device which comprises a radio-frequency generator, a power lead and a return lead, means for coupling the power lead and the return lead to the radio-frequency generator, an active electrosurgical electrode, means for coupling the power lead to the active electrosurgical electrode to power the active electrode, a passive electrode, means for coupling the passive electrode to the return lead, alternate path return means for coupling the return lead to ground at a point between the passive electrode and the radio-frequency generator, and means in the alternate path return means for indicating a predetermined radio-frequency return in the alternate path return means.

2. A device as in claim 1 where said indicating means in the alternate path return means is sensitive to rms current.

3. A device as in claim 1 including frequency sensitive impedance means disposed in series with said indicating means in the alternate path return means having a first value of impedance at 60 Hz and a second value of impedance at a frequency substantially greater than 60 Hz where the second value is less than that of the first value.

4. A device as in claim 3 where said frequency substantially greater than 60 Hz is a radio frequency corresponding to that of the radio-frequency generator.

5. A device as in claim 3 where said frequency sensitive impedance means is a capacitor.

6. A device as in claim 5 where the value of said capacitor is about 2000 pf.

7. A device as in claim 1 including timing means responsive to said indicating means in the alternate return path means for preventing the application of the output of said radio-frequency generator to said active and passive electrodes for a predetermined period of time after the indicating means indicates said predetermined radio-frequency return.

8. A device as in claim 1 where said means for coupling the power and return leads to the radio-frequency generator comprises a transformer.